This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A009008 #25 Oct 27 2023 21:10:53
%S A009008 1,1,1,-23,-415,849,421089,16027897,-602344127,-137830187103,
%T A009008 -6375572516543,1282077224074761,294398207479497377,
%U A009008 6767832711454751473,-10535904130516747834591,-2468712006908963695579879,172926818125145929773139073
%N A009008 Expansion of e.g.f.: 1/cos(sin(x)) (even-indexed coefficients only).
%H A009008 Alois P. Heinz, <a href="/A009008/b009008.txt">Table of n, a(n) for n = 0..100</a> (first 51 terms from Vincenzo Librandi)
%t A009008 f[x_] := Sec@Sin[x]; Table[Derivative[2*n][f][0], {n, 0, 16}] (* _Arkadiusz Wesolowski_, Aug 18 2012 *)
%t A009008 With[{nmax = 50}, CoefficientList[Series[1/(Cos[Sin[x]]), {x, 0, nmax}], x]*Range[0, nmax]!][[1 ;; -1 ;; 2]] (* _G. C. Greubel_, Jul 21 2018 *)
%o A009008 (PARI) x='x+O('x^50); v=Vec(serlaplace(1/cos(sin(x)))); vector(#v\2,n,v[2*n-1]) \\ _G. C. Greubel_, Jul 21 2018
%K A009008 sign
%O A009008 0,4
%A A009008 _R. H. Hardin_, _Simon Plouffe_
%E A009008 a(16) from _Arkadiusz Wesolowski_, Aug 18 2012